A common form of internal combustion engine is the air-cooled reciprocating engine with horizontally opposed cylinders. These engines were designed to be long-lived, low horsepower devices that could be easily serviced and maintained. Over the span of several decades, as the amount of freeway driving increased markedly, the greater average velocity of auto travel demanded a corresponding increase in engine horsepower output. To satisfy this demand, these aircooled engines were provided with greater cylinder displacements, while the engine block and ancillary parts remained relatively unchanged.
Axiomatically, an increase in power output is accompanied by an increase in heat generated in the engine. An important aspect of the cooling system is the oil cooler, which provides cool oil to moving parts which undergo the highest wear and generate the most heat. Although the air cooling system has proven to be sufficient to cool the cylinders and the engine block, it has been found, through many unfortunate engine breakdowns, that the oil cooling system cannot support the increased power of the engine. That is, the oil cooling radiator within the air shroud of the engine radiates so much heat that the nearby engine parts are not adequately cooled. Thus, a common occurrence is that nearby valves or bearings heat up and burn out, causing sudden, disasterous breakdowns which are expensive to repair.
Although a larger capacity, original equipment oil cooler designed to accommodate the modern engine prior output would obviously solve this problem, such a cooler has not been forthcoming from the manufacturers for many years. Millions of engines now in operation are subject to such breakdown, and are in need of modification. One such modification attempted in the prior art involved the diverting of a portion of the oil flow into an additional oil cooling radiator disposed in the cooling-air stream. These devices failed partly due to the fact that the additional radiator heated the airstream so that the engine as a whole was overheating.